Electric incandescent lamp



' AVAILABLE COP June M, 194% A. DE GRAAFF 9 ELECTRIC INCANDESCENT LAMP Filed Oct. 27, 1938 CONN/NS NITROGEN.

Inventov- Antonius de Graaff,

His Attor'neg.

il atcnteri June it, i

itr

e g; earner tting acorns? recast? apnea-arc rscan ascanr new Antonius dc @raah, Eindhoven, Netherlands, as signer to General Electric @cmpany, a corpora tion oi blew Yuri: V

smile-statements rest, 'fierlal no. ceases linthe Netherlands Novenitmr 2, H93? a @iiainio. (or. ire-rel My invention relatesin general to electric incandescent lamps comprising a tungsten or other refractory metal filament mounted within a sealed envelope containing a gaseous filling corn-- f posed at least partly of nitrogen. More .par-

ticularly;- my invention relates to socalled played as a getter in electric incandescent. lamps having a gas filling that contains a certain qua'n tity of nitrogen for the reason that the zirconium,-

in addition to absorbingthe impurities in tl-ie gas filling and the traces of residual gas, also j absorbs the nitrogen in the gas filling. This absorption of the nitrogen, is objectionable since the presence of nitrogen. in the bulb is desirable for'the proper operation of the lamp. As is well known, the nitrogen: illthfi' ga's filling serves to '1 give a suitably high value to the breakdown voltage of'the gasilllingwhich, as a rule,.con-

' sists'ior a great part of one or several rare gases such as ltrypton or argon. If in such a lamp zirconium were to beadded, then the possibility .might exist, because of the afinity oi zirconium for nitrogen, that the nitrogen would be absorbed by the zirconium. The absorption of the nitrogen might then result in the occurrence of a premature breakdown between the leading-in wires in the lamp.

One object of my invention is to provide a getter which will eilectively absorb the residual gases in an electric incandescent-lamp to there.-'

40 by reduce blackening oi the lamp bulb and also to prevent failure of the lamp on account of the attack of the filament by water vapor.

Another object of my invention is the provision of a getter, in an electric incandescent lamp having a gaseous filling consisting partly .of nitrogen, which will effectively absorb the impurities in the gaseous filling and the traces of residual gas but not the nitrogen.

Still another object of my invention is the provision of a gas-fllled electric incandescent lamp with a getter located at a point in the lampbulb where the temperature, during lamp operation, is within a certain definite range whereby the getter will eflfectively absorb the impurities in the gaseous filling and the traces oi residual gas but not the nitrogen containedin the gaseous filling.

Wither objects and advantages of my invention will appear from the .follcliwing description of a species thereof.

The applicant has found that zirconium will or will not absorb certain gases depending upon the temperature to which it is heated. Conseuuently, a so-called selective absorption "by the mrconiugm takes place. This fact is utilized in the l pfia'ccarding to the invention-in order to absoi'bjthe hydrogen or hydrogen compounds which are always located in the metal parts of the lamp, such as the nickel current supply wires and the like, and which are liberated during the "operation of the lamp. The hydrogen and hydrogen compounds have a destructive effect on the material of the filament, such as tungsten, which. effect-is unfavorable to the properties of the filament. Thus, the liberated hydrogen, together with the traces of oxygen which are always present in the lamp, will result in the socalled water cycle, while a certain hydrogen compound, such as a hydrocarbon, will, in addition, carburize the filament and thereby-give the lamp a lesser degree of resistance to shocks. The resuit is that the filament failsprematurely.

' in the lamp according to the invention, in which a gas filling is present which contains nitrogen, some metallic bodies of zirconium are located at a point in the lamp at which the temperature is of the order of magnitude of ZOO-600 C. when the lamp is inoperation. Within this temperature zone, the zirconium will bind the liberated hydrogen and. hydrogen compounds, but the temperature of the zirconium is not high enough for a noticeable absorption of the nitro-= gen which is present in the lamp and which is necessary for its proper operation. The zirconium parts can, according to the invention, be provided for instance on the stem'press of the lamp. In the case of automobile lamps, such as shown in Patent 1,716,048,A. graves, which have a filament that is partly surrounded by a shield, the zirconium can be conveniently applied to this shield. It is also possible to provide the zirconium at a suitable point on the current supply wires. The zirconium can be placed in the lamp in the pulverulent state'or in any other suitable form, such as in the form of a wire, strip, or foil. It is obviously desired to degasiiy the zirconium as thoroughly as possible before it is used. This degasiiication is carried out pref:- erably by annealing the mrconium in a high vacuum.

til

Regardless of the fact that the filament is attacked by the hydrogen or hydrogen compounds, the disadvantage occurs, when the invention is not utilized, that due to the water cycle the lamp blackens relatively more rapidly whereby a considerable portion of the light emitted by the filament is absorbed. Especially when the available bulb surface is small is this disadvantage of importance. This is particularly the case in those lamps in which a filament with a rather high power consumption is used in a small bulb, which is the case, for instance, in automobile lamps. The blackening is particularly evident in that type of automobile lamp in which the filament is partly surrounded by a shield, because in such lamps very many metal parts are located in a relatively small bulb volume. In such lamps, the use of zirconium according to the invention is highly advantageous.

For a further understanding of my invention, reference may be had to the drawing which is a plan view of an automobile" lamp of the type referred to above.

Referring to the drawing, the lamp comprises a glass bulb Ill containing a gaseous atmosphere comprising nitrogen and enclosing a major filament II and a minor filament H, with a metal shield l3 located under the said minor filament. The said filament H is connected to leads l4 and I5, and filament I2 is connected, through shield It, to common lead II and tolead ii. The said leads II, II and I! extend through a glass stem.

IT to contacts on the base ll. For obtaining the gettering effect referred to above, a quantity oi zirconium I8 is preferably disposed on the stern II. If desired, the zirconium l9 may be disposed on the shield It, as indicated by dotted lines.

Letters Patent of the United States is:

1. An electric incandescent lamp comprising an envelope having a, gas filling containing nitrogen, and a body of metallic zirconium within said envelope,,said body being located at a point in said envelope at which the temperature, during operation of the lamp, is of the order of magnitude of 200 C. to not over about 600 C. whereby the heated zirconium abjsorbs hydrogen and hydrogen compounds-present in the lamp but does not appreciably absorb the nitrogen in the lamp. 2. An electric incandescent lamp comprising an envelope having a gas filling containing nitrogen, a filament insaid envelope, a stem extending into said envelope for supporting said filament, and a body of metallic zirconium located within said envelope on said stem where it is heated to a temperature of .the order of 200 C. to not over about 600 C. whereby the heated zirconium ab- What I claim as new and desire to secure by sorbs hydrogen and hydrogen compounds present in the lamp but does not appreciably absorb the nitrogen in the lamp.

. ANTONIUS or: GRAAFF. 

